Determining flow rates with thermal sensors

Abstract

A thermal inkjet printing device includes a fluidic die having a thermal sensor and a processor coupled to the fluidic die. The processor is to receive temperature data from the thermal sensor and determine a flow rate of liquid printing agent through the fluidic die based on the temperature data and an operating parameter for the fluidic die.

What is claimed is: 
     
         1 . An inkjet printing device, comprising:
 a fluidic die comprising a first thermal sensor; and   a processor coupled to the fluidic die, the processor to:
 receive temperature data from the first thermal sensor; and 
 determine a flow rate of fluid through the fluidic die based on the temperature data and an operating parameter for the fluidic die. 
   
     
     
         2 . The inkjet printing device of  claim 1 , wherein the operating parameter comprises a warming temperature for the fluidic die or a warming frequency for the fluidic die. 
     
     
         3 . The inkjet printing device of  claim 1 , comprising a fluidic module comprising a plurality of fluidic dies, each of the fluidic dies comprising a thermal sensor, wherein the processor is to:
 receive temperature data from the thermal sensors; and   determine a flow rate of fluid through the fluidic module based on the temperature data from the thermal sensors and an operating parameter for the fluidic module.   
     
     
         4 . The inkjet printing device of  claim 3 , wherein the flow rate through the fluidic module comprises a sum of flow rates through the fluidic dies. 
     
     
         5 . The inkjet printing device of  claim 1 , wherein the fluidic die comprises:
 a flow channel formed in a back side of a substrate;   a membrane region positioned between the flow channel and a front side of the substrate;   a plurality of fluid feed holes in the membrane region, each fluid feed hole in communication with the flow channel and the front side of the substrate;   a second thermal sensor disposed on the membrane region of the substrate;   a third thermal sensor disposed on the substrate on a first side of the membrane region; and   a fourth thermal sensor disposed on the substrate on a second side of the membrane region,   wherein the processor is to:
 receive temperature data from the thermal sensors; and 
 determine a flow rate of fluid through the fluidic die based on the temperature data from a subset of the thermal sensors and an operating parameter for the fluidic die. 
   
     
     
         6 . The inkjet printing device of  claim 1 , wherein the first thermal sensor comprises a thermal sense resistor. 
     
     
         7 . A method, comprising:
 receiving temperature data from a thermal sensor disposed on a fluidic die; and   determining a fluid flow rate for the fluidic die based on the temperature data and an operating parameter for the fluidic die.   
     
     
         8 . The method of  claim 7 , wherein the operating parameter comprises a warming temperature for the fluidic die or a warming frequency for the fluidic die. 
     
     
         9 . The method of  claim 8 , comprising:
 determining a relationship between the temperature data and the flow rate of fluid through the fluidic die by:
 selecting a target warming temperature for the fluidic die; 
 applying a level of power to the fluidic die less than a threshold level of power sufficient to reach the target warming temperature; and 
 selecting a warming frequency that maximizes a range of temperature values that represent a range of flow rates. 
   
     
     
         10 . The method of  claim 7 , comprising:
 receiving temperature data from a plurality of thermal sensors disposed on a plurality of fluidic dies of a fluidic module; and   determining a flow rate of fluid through the fluidic module based on the temperature data from the thermal sensors and an operating parameter for the fluidic module.   
     
     
         11 . The method of  claim 10 , wherein the flow rate through the fluidic module comprises a sum of flow rates through each of the fluidic dies. 
     
     
         12 . A non-transitory, machine-readable medium containing instructions that, when executed by a processor, cause the processor to:
 receive temperature data from a thermal sensor disposed on a fluidic die; and   determine a flow rate of fluid through the fluidic die based on the temperature data and an operating parameter for the fluidic die.   
     
     
         13 . The non-transitory, machine-readable medium of  claim 12 , wherein the operating parameter comprises a warming temperature for the fluidic die or a warming frequency for the fluidic die. 
     
     
         14 . The non-transitory, machine-readable medium of  claim 12 , wherein the instructions, when executed, cause the processor to:
 receive temperature data from a plurality of thermal sensors disposed on a plurality of fluidic dies of a fluidic module; and   determine a flow rate of fluid through the fluidic module based on the temperature data from the thermal sensors and an operating parameter for the fluidic module.   
     
     
         15 . The non-transitory, machine-readable medium of  claim 14 , wherein the flow rate through the fluidic module comprises a sum of flow rates through the fluidic dies.